@TimArmstrong You can follow the link to call Postman Pro APIs to fetch the collections and environments (If required for Newman run) at the time of Newman run. (No need to store them in any file)
Few points:-
You are required to have a valid API key to fetch collection/environments
The uid is the user_id-collection_id which you have to provide to fetch the specific collection for Newman run.
My problem was I had not wrapped my URL in double quotes and so I suspect the shell was helping me by further interpreting my command and make a mess of things.